The Brain of the Sleeping Cat: Dynamics of Electrical Signals

Abstract

There are several possible classifications to describe the various stages of sleep in the cat, which spends about two-thirds of its day asleep. The process of falling asleep for the cat follows a characteristic course in time and is recognizable by easily observable external cues. Typically, the animal curls up into a ball with its neck in a bent position. The flexing of the neck is a clear sign that the neck muscles retain some tonus; i.e., they are not completely relaxed. In this position, the cat lapses into a light sleep from which it is easily awakened (Jouvet 1964). Jouvet states that the first stage of sleep, or light sleep, is characterized by a slackening of electrical activity in the cortex and subcortical structures, by the occurrences of “spindles,” or groups of sharp jumps in the brain waves, and by the retention of muscular tension. Ursin (1971) makes a classification in which the so-called slow wave sleep (SWS) stage has two aspects: light slow wave sleep characterized by 12- 14 Hz high-volt age sleep spindles and some 1–4 Hz high-volt age slow waves on a low-voltage background. Deep slow wave sleep consists of at least 10 sec of slow waves and spindles covering half of the recording period.